596 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1953 



temperatures. The heating for three hours at 175°C produces the degree 

 of relaxation expected over a 40-year period. By examining and esti- 

 mating the size of the gas-tight areas after this process, the necessity 

 for maintaining the intimate minimum gas-tight area demanded by 

 General Requirement 3 is considered to be met. Item 6, the remeasure- 

 ment of resistance is further confirmation of proper performance after 

 relaxation. 



For the measurement of resistance, and barrier films a circuit is used 

 as sho^vn on Fig. 1. With Ri set at "a," R2 is adjusted so that the voltage 

 of about 25 microvolts is applied across R^ before the connection to be 

 measured is inserted. This voltage is low enough to insure the absence 

 of a film and at the same time gives a convenient reading on the test 

 set. If the millivoltmeter drops to approximately when the connection 

 is inserted it indicates that no barrier film exists at the connection. The 

 current is then increased to 100 milliamperes by means of the potenti- 

 ometer, Ri, and the resistance is determined from the millivoltmeter 

 reading. Since most of the measured resistance is in the wire rather than 

 in the connection the important criterion of quality is the variation in 

 resistance as the wire is moved relative to the terminal. If the variation 

 in resistance of the connection does not exceed two milliohms when 

 the wire is moved back and forth the connection is considered to be 



—TERMINAL 



STRIPPER 



Fig. 2 — Stripping force test for solderless connection. (1) The connection 

 shall consist of six turns minimum of which at least four are close wound. (2) The 

 connection shall be capable of withstanding a stripping force, F, of at least 30()0 

 grams applied as shown. (3) The wire shall be capable of being unwrapped from 

 a terminal without breaking. 



